1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.configuration2.reloading;
18
19 /**
20 * <p>
21 * An interface to be implemented by objects which can detect whether a reload operation is required.
22 * </p>
23 * <p>
24 * This interface is used by a {@link ReloadingController} object. When a reloading check is to be performed, it is
25 * delegated to a concrete implementation. The implementation decides whether (specific) criteria for a reload are
26 * fulfilled, so that the controller can react accordingly.
27 * </p>
28 * <p>
29 * This interface does not define how a check for a reload is performed. This is completely up to a concrete
30 * implementation. There is just one method for executing the check and one method to notify the
31 * {@code ReloadingDetector} that the reload actually happened; this method can be used to reset the internal state so
32 * that the conditions for the next reload can be detected.
33 * </p>
34 * <p>
35 * When used together with {@code ReloadingController} an implementation does not have to be thread-safe. The controller
36 * takes care for synchronization so that an instance is accessed by a single thread only.
37 * </p>
38 *
39 * @since 2.0
40 */
41 public interface ReloadingDetector {
42 /**
43 * Checks whether all criteria for a reload operation are fulfilled. This method is called by external components to
44 * find out when reloading should take place.
45 *
46 * @return <b>true</b> if a reload operation should be performed, <b>false</b> otherwise
47 */
48 boolean isReloadingRequired();
49
50 /**
51 * Notifies this object that a reload operation has been performed. This method is called after
52 * {@code reloadingRequired()} has returned <b>true</b>. It can be used to reset internal state in order to detect the
53 * next reload operation.
54 */
55 void reloadingPerformed();
56 }